Axial piston pumps or motors



A1182 17, 1955 o. H. THoMA 3,200,762

AXIAL PISTON PUMPS OR MOTORS Aug. 17, 1965 o. H. THOMA 3,200,762

AXIAL PISTON PUMPS OR MOTORS Filed Dec. 17, 1963 2 Sheetss-Sheei'l 2 FIG. 3

INVENTORu 05W/M0 M 7"//0//4/4 United States Patent 3,266,762 AXAL PHSTN PUMPS @R MTRS @swald H. Thoma, Charlton Kings, Cheltenham, England,

assigner to Unipat ALG., Glarus, Switzerland, a cornpany or Switzerland Filed Ecc. 17, 1963, Ser. No. 331,291 `Claims priority, application Germany, Dec. 19, 1962, U 9,464; Feb. 27, 1953, U 9,614 8 Claims. '((Cl. 10E-162) This invention relates to axial piston pumps or motors of the kind .in which `a rotary cylinder block contains cylinder bores arranged regularly in the block with their axes parallel to the axis of rotation, a pair of pistons in each cylinder extending from opposite ends of the cylinder block, and inclined or inclinable plates or the like located one at each end of the cylinder block against which the projecting ends of the pistons are arranged to react during cylinder block rotation. More particularly, `although not exclusively, the invention concerns a lowspeed high-torque axial piston motor which, for example, might rotate at .about two hundred revolutions per minute `and it `might develop driving torque of ten thousand loot pounds at an operating hydraulic pressure of about 5,000 p..s.i.

In accordance with the present invention, an axial piston pump or motor comprises a rotary cylinder block which contains cylinder bores arranged regularly in the block parallel to the axis of rotation, a pair of pistons in each cylinder extending from opposite ends of the cylinder block, an inclined or inclinable plate located at each end of the cylinder block against which the projecting ends of the pistons are :arranged to react, a drive shaft fast with the block extending from one end oi the cylinder block t-hrough a central hole in the plat-e at that end, a `ifirst bearing for radial loads locating the drive shaft for rotation relatively to the plates, a stub axle fast with the block extending from the opposite end of the block through a central hole in the other plate, a second bearing `for radial loads locating the stub axle for location relatively to the plates, passages for supplying liquid to and from the cylinders extending through the stub axle yand valve means associated with the passages for sequentially connecting the cylinders alternately to low and high pressure zones during cylinder block rotation.

The valve lmeans may be located with-in the stub axle and may comprise a stationary member extending into a relcess within the stub axle, this stationary member having a pair of passages adapted `for connection to the low and high pressure zones, a valve surface forming part of the cylinder block int-o which passages open one from each cylinder, `a valve member secured to the stationary member so as not to rotate relatively to the stationary member about the block rotation axis but otherwise free to move, and hydraulic balancing means to urge the valve member axially into contact with the valve surface so 'that rotation of the cylinder block will alternately connect the passages in the stationary member with the passages in the block, The pump or motor may include a casing surrounding ,the cylinder block, the plate forming part of the casing and directly supporting the bearings for the drive shaft and the stub axle.

lFurther in accordance with the present invent-ion an axial piston pump may comprise a rotary cylinder block which contains cylinder bores arranged regularly in a block parallel to the .axis oi rotation, a pair of pistons in each cylinder extending from opposite ends of the cylinder block, having inclined or inclinable plate located at each end of the cylinder block against which the projecting ends of the pistons are arranged to react, a drive shaft fast with the block extending from one end of the block through a central hole in the plate at that end, a

FlriceN first bearing for radial loads locating the drive shaft for rotation relative-ly to the plates, a stub axle fast with the block extending .trom the opposite end of the block, a second bearing for radial forces locating the stub axle for rotation relatively to the plates, a face valve co-operating with the block for supplying liquid to and from the cylinders, and an end thrust bearing acting directly or indirectly on the block to .oppose axial thrust produced on the block by the face valve.

The thrust bearing may be a ball bearing and may cooperate With a iiange fast with the cylinder block. The flange is preferably of such thickness that it will ydeilect very slightly under the iaxial load to the extent to load all the balls in the bearing to substantially equal extent.

One embodiment of the invention for use as a lowspeed high-torque motor will be described with reference to the accompanying drawings, in which,

FIGURE l is a longitudinal cross-section through the motor,

FIGURE 2 is a plan View of the valve member of FIG- URE 1,

FIGURE 3 is a 'cross-section through the valve member at right angles to the section appearing in FIGURE 1, and

FlGURE 4 is a perspective view of part of the casing of the motor of FIGURE l before .assembly into position.

Referring to FIGURE l, a rotary cylinder block 1 contains a plurality of cylinder bores 2 regularly arranged inthe Ablock parallel to the axis of rotation. Within each cylinder bore a pair of pistons 3 and 4 ar-e mounted for reciprocation. These pis-tons project from the opposite end surfaces of the cylinder block 1. Each of the pistons 3 carries at its outer end a slipper 5 mounted by means of a ball socket 6 in the end of piston 3. The slipper 5 engages against an inclined dat surface 7 formed on a plate il. An axial bore 9 in the piston 3 communicates with an axial bore 111 in the slipper 5 which, in turn, communicates with a recess 1-2 within the surface 13 of the slipper which engages the inclined surface 7. The crosssectional area of the recess 12 is arranged to be of slightly smaller effective `area than the cross-section of the cylinder 2 so that pressure in the cylinder 2 when it acts in the recess i12 will almost completely balance the slipper 5 on lthe surface 7.

Similarly, the pistons 4 each include a slipper 14 having a ball joint 15 formed in the end of the piston 4. The slippers 14 engage an inclined surface 16 formed on an end plate 17. Axial passages 18 and 19 through piston and slipper -feed pressure from the cylinder 2 to a recess 21 in the surface 22 of the slipper y14 which engages the surface 16. The area of the recess 2.1 is slightly less than the cross-section of the cylinder 2.

Within each cylinder 2 a compression spring 23 acts between the two pistons 3 and 4 to urge them apart so that they engage the inclined sur-.faces 'i and 16.

The end plates 8 and 17 are secured in a cylindrical casing 24, the end plate being retained by iianges 25 at the ends of .the `casing 24. As shown in FIGURE 4 it will be seen that the casing 24 is formed in two parts divided in a plane passing through the longitudinal axis, adjoining edges of the casing being provided with flanges 25 which are secured together by bolts.

From one end of the cylinder block 1 extends a drive shaft 27 which is integral with the block ll. This shaft passes through a central hole 28 in the end plate 8 and `a roller bearing 29 in the hole 23 locates the shaft 27 for rotation.

At the opposite end of the cylinder block 1 a hollow stub axle 31 extends axially, being secured in position by a number of bolts 32. The stub axle 31 is located in position on the end of the block by a projecting portion 33. The end sunface 34 of the portion 33 is ground flat to a high degree of accuracy to a plane at right angles to the rotation laxis. The stub axle enters a central hole 35 i-n the end plate 17 and is located for rotation therein by la roller bearing 36. A cap 37 is secured by a bolt 33 on the end plate 17 over the central hole 35 and 'an integr-al projection 39 on the cap 37 enters the recess in the stub axle 31. A pair of passages 41 and 42 extend through cap 37 and extension 39 and externally of the motor these passages are connected respectively to pipes 33 land 347 which extend toa hydraulic pump.

Internally of 4the stub axle the passages 41 and 4Z terminate in counterbores in each of which a sleeve, respectively 45 and 46, is mounted. A floating valve plate 47 is located in the space between the inner end of projection 39 and the surface 34 and is engaged in posi-tion by bores 4S and 49 which lit on sleeves 45 and 46. The bores 48 and 49 open into kidney shaped por-ts 51 and 52. A plurality of passages 53 extend within the block 1 from the centre positions of the cylinders 2 and terminate as regularly-spaced ports 54 in the surface 34 for co-opera-tion with the kidney ports 51 and 52. Hydraulic pressure acting in the bores 48 and 49 will produce forces on the valve plate 47 to balance in part the parting force at the kidney ports tending to urge the valve plate away from the surface 34. Also in connection with the kidney ports are a further pair of recesses 55 and 56 located in a plane at right-angles to the cross-section shown in FIGURE 1. These recesses are shown more particularly in FIGURES 2 and 3. These recesses cooperate with blind recesses 57 Aand 58 in the projection 39 and sleeves 59 and 61 inter-connect the-se recesses. The function of these recesses is to provide an extra balancing area so that the valve plate 54 may be held hydraulically against the face 34 with a force slightly greater 4than the parting force generated at the kidney ports. Springs 62 within the sleeves 59 and 61 act to urge the valve plate 47 against the surface 34. The provision of a pair of balancing recesses located behind each kidney port, as shown in FIGURE 2, will ensure that the centre of pressure at the kidney port coincides Asubstantially with the centre of pressure produced in the recesses. In this way it may be ensured that the action of hydraulic pressure in either of the kidney ports will not tend to tip the valve plate. Since the valve plate is located only by the four sleeves 45, 46, 59, 61 it is held against rotation relatively to the projection 39, but at the same time it is free to move in all other senses, although to a limited extent relative to the member 39. In particular the valve plate may move axially into contact with the valve plate 34 and may tip small amounts during rotation of the cylinder block to accommodate any inaccuracies in the machining of the surface 34. The four sleeves 45, 46, 59 and 61 are provided with sealing rings so that they may engage in a Huid-tight manner in the co-operating recesses in the valve plate and the projection 39.

Because the two pistons in each cylinder are of the same diameter the pistons themselves can exert no hydraulic thrust in the axial sense on the cylinder block 1. However, the hydraulic reaction in the axial direction is exerted on the cylinder block 1 by the valve plate 47 and this axial thrust is tnansmi-tted from the block to the end plate 8 through the medium of a Iball thrust race 63. This thrust race reacts against a ilange 64 extending peripherally around the drive shaft 27 where it joins the cylinder block 1. This flange has radial and axial dimensions suicient to permit it to bend elastically to a very slight extent under the axial thrust from the valve plate. Such bending will take up any non-uniformity in the machining of the seatings of the ball race 63 and thus help to ensure that the axial thrust is distributed evenly over the whole ball race 63.

For operation of the motor described, the two hydraulic connections 42 and 43 are connected to the inlet and delivery connections of a high pressure hydraulic pump to form a substantially closed hydraulic circuit with the pump. This close-d hydraulic circuit is maintained primed at low pressure by means of a low pressure boost pump. According to the direction of pumping one of the connections 43 or 44 will remain at the low priming pressure and the other of these connections will be at much higher pressure. The cross-section through projection 39 and valve plate 47 is deliberately drawn in a different plane from the section through the remainder of the motor in order to illustrate the hydraulic connections lto the valve plate, and, in fact, the ports 54 in the cross-section of the motor of FIGURE 1 lie in Y between the ends of the kidney ports 51 and 52. Assume that the higher pressure is fed to the port 43, it will be seen that such high pressure will attain access to the kidney port 51 and into the recesses 43 and 56. The valve plate, therefore, will be hydraulically urged to the surface 34 to make hydraulic connection with the ports which coincide with the port 51. In .the normal timing of the valve plate 47 the port 51 will coincide with ports 54 on yall cylinders whose pistons, having regard to the direction of rotation, are moving outwardly from their cylinders by vir-tue of the inclined surfaces '7 and 16. The kidney port 52 will be connected with all ports 54 whose associated pistons are moving inwardly. The driving torque is generated o-n the cylinder block 1 by the action of high pressure from kidney port 51 on the outwardly moving pistons which, as a result of the inclined surfaces, 7 and 16, will genenate a tangential force on these pistons causing the cylinder block to rotate. The combination of the tangential force on the outwardly moving pistons with the torque that is exerted by the drive shaft 27 -on the load will give a substantial radial thrust reaction at the roller bearings 29 and 36. Since these bearings are located one at either end of the cylinder block they will react almost directly against the slippers which produce the tangential force and will prevent any substantial tipping moments being applied to the cylinder block. The axial forces acting on the outwardly moving pistons will be reacted to the end plates 8 and 17 and on to the flanges 25 of the casing 24 and will therefore hold the casing 24 in tension between the anges 25. The casing 24 and the end plates 8 and 17 are preferably made of substantial size in order adequately to resist these axial forces.

' The direction of rotation of the motor may be reversing the high and low pressure supplies to the connections 43 and 44.

Whilst in the described embodiment the valve has been lshown acting on the end surface 34 of the block 1 the invention is in no way limited to the axial location of lthe valve. For example, the valve could be located completely within the cylinder block or, alternately, it could be located on the outer end of the stub axle 31. Further, within the scope of the present invention the valve need not necessarily be of the face type but could equally well be of the pintle type.

What I claim is:

1. An axial piston pump or motor comprising a rotary cylinder block which contains cylinder bores arranged regularly in the block parallel to the axis of rotation, a pair of pistons in the cylinder extending from the opposite ends of the cylinder block, and inclined plate located at each end of the cylinder block against which the projecting ends of the pistons are arranged to react, a drive shaft fast with the block extending from one end of the cylinder block to a central hole in the plate at that end, a rst bearing for radial loads located the drive shaft for rotation relatively to the plates, a stub axle fast with the block extending from the opposite end of the block through a central hole in the other plate, a second bearing for radial loads locating the stub axle for rotation relatively to the Y plate, passages for supplying liquid to and from the cylinders extending through the stub axle, and valve means asscciated with the passages for sequentially connecting the cylinders through the passages alternately to low and high pressure zones during the cylinder block rotation.

2. An axial piston pump or motor as claimed in claim l, wherein the valve means is located within the stub axle.

3. An axle piston pump or motor as claimed in claim 2, wherein the valve means comprises a stationary member extending into a recess within the stub axle, this stationary member having a pair of passages adapted for connection to the low and high pressure zones, a valve surface forming part of the cylinder block into which passages open one from each cylinder, a valve member secured to the stationary member so as not to rotate relatively to the stationary member about the block rotation axis but otherwise free to move, an hydraulic balancing means to urge the valve member axially into contact with the valve surface so that rotation `of the cylinder block will alternately connect the passages in the stationary member with the passages in the block.

4. An axial piston pump or motor as claimed in claim 3, wherein the stub axle is detachably secured to the block over the valve surface.

5. An axial piston pump or motor as claimed in claim 1 including a casing surrounding the cylinder block, the plates forming part of the casing and directly supporting the bearings for the drive shaft and the stub axle.

6. An axial piston pump or motor as claimed in claim 5, wherein the casing is formed in two semi-cylindrical parts detachable together so that the flanges engage the plates.

7. An axial piston pump comprising a rotary cylinder block which contains cylinder bores arranged regularly in the cylinder block parallel to the axis of rotation, a pair of pistons in each cylinder extending from the opposite ends of the cylinder block, an inclined plate located at each end of the cylinder block against which the projecting ends of the pistons are arranged to react, a drive shaft fast to the block extending from one end of the block to a central hole in the plate at that end, a rst bearing for radial loads locating the drive shaft for rotation relatively to the plates, a stub axle fast with the block extending from the opposite end of the block, a second bearing for radial loads locating the stub axle for rotation relatively to the plates, a face valve cooperating with the block for conveying fluid to and from the cylinders, and an end thrust bearing acting directly or indirectly on the block to oppose axial thrust produced on the block by the face valve.

8. An axial piston pump as claimed in claim 7, wherein the end thrust bearing is a ball bearing cooperating with the flange fast with the cylinder block, the ilange being of such radial and axial dimensions as to be slightly formable within the elastic limits of the material in order to spread the axial thrust of the valve evenly over the ball bearing.

References Cited by the Examiner UNITED STATES PATENTS 2,484,337 lO/49 Ferris 103-162 2,617,360 11/52 Barker 103-162 3,043,233 7/62 Rumsey 103-162 3,059,432 10/62 Thoma 103-162 DONLEY J. STOCKING, Primary Examiner.

LAURENCE V. EFNER, Examiner. 

1. AN AXIAL PISTON PUMP OR MOTOR COMPRISING A ROTARY CYLINDER BLOCK WHICH CONTAINS CYLINDER BORES ARRANGED REGULARLY IN THE BLOCK PARALLEL TO THE AXIS OF ROTATION, A PAIR OF PISTONS IN THE CYLINDER EXTENDING FROM THE OPPOSITE ENDS OF THE CYLINDER BLOCKU, AND INCLINED PLATE LOCATED AT EACH END OF THE CYLINDER BLOCK AGAINST WHICH THE PROJECTING ENDS OF THE PISTONS ARE ARRANGED TO REACT, A DRIVE SHAFT FAST WITH THE BLOCK EXTENDING FROM ONE END OF THE CYLINDER BLOCK TO A CENTRAL HOLE IN THE PLATE AT THAT END, A FIRST BEARING FOR RADIAL LOADS LOCATED THE DRIVE SHAFT FOR ROTATION RELATIVELY TO THE PLATES, A STUB AXILE FAST WITH THE BLOCK EXTENDING FROM THE OPPOSITE END OF THE BLOCK THROUGH A CENTRAL HOLE IN THE OTHER PLATE, A SECOND BEARING FOR RADIAL LOADS LOCATING THE STUB AXLE FOR ROTATION RELATIVELY TO THE PLATE, PASSAGES FOR SUPPLYING LIQUID TO AND FROM THE CYLINDERS EXTENDING THROUGH THE STUB AXLE, AND VALVE MEANS ASSOCIATED WITH THE PASSAGES FOR SEQUENTIALLY CONNECTING THE CYLINDERS THROUGH THE PASSAGES ALTERNATELY TO LOW AND HIGH PRESSURE ZONES DURING THE CYLINDER BLOCK ROTATION. 